In recent years, an integration degree in a large-scale integration (LSI) system has increased year by year along with sophistication in a system and finely-divided processes. Reflecting this, an equipment system which conventionally includes a plurality of chips are currently being made into a single chip. However, it is particularly difficult for an analog block having a sensor system to be made into a single chip. In the analog block having a sensor system, a fine analog signal is processed. Accordingly, a semiconductor process which requires a sensor to increase its susceptibility and a process for improving the fine-division at a low cost are not necessarily the same process.
For example, FIG. 21 shows a sensor integrated circuit (IC) and a microcomputer in a conventional technique. FIG. 21 shows an example which includes two chips, such as a sensor ICX and a microcomputer Y, an output terminal X3 for outputting a signal from the sensor ICX, and an input terminal X4 for inputting a signal into the sensor ICX, and the output terminal X3 and the input terminal X4 are connected to the microcomputer Y via a signal line (See Patent Literature 1, for example).
FIG. 22 is a diagram which shows a magnetic-field detection circuit according to a conventional technique. As shown in FIG. 22, processing described below is performed for improving temperature characteristics of the sensor IC. An output OUTA from a hall element HAL1, which is amplified by an amplifier circuit AMP1, is inputted in a comparator circuit CMP1. In addition, a voltage reference circuit BL1 includes only a voltage divider circuit which generates reference voltages VTH1 and VTH2, and performs temperature compensation. One of the reference voltages VTH 1 and VTH2 generated in the voltage reference circuit BL1, which has a temperature coefficient approximately equal to that of the output OUTA, is selected by a switching circuit SW1, and the selected reference voltage is inputted in the comparator circuit CMP1 as a reference voltage OUTB.
The comparator circuit CMP1 compares the output OUTA and the reference voltage OUTB so as to detect the magnetic field. Specifically, a circuit is added which includes the switch circuit SW1 and the reference voltage circuit BL1 and cancels the temperature characteristics of the output OUTA, as shown in FIG. 22. Patent Literature 2, for example, discloses a method used for improving performance of the individual sensor IC, using the above configuration. In the following description, a technique disclosed in Patent Literature 2 is also referred to as a conventional technique B.